// Formatting library for C++ - experimental format string compilation
//
// Copyright (c) 2012 - present, Victor Zverovich and fmt contributors
// All rights reserved.
//
// For the license information refer to format.h.

#ifndef ABEL_STRINGS_INTERNAL_COMPILE_H_
#define ABEL_STRINGS_INTERNAL_COMPILE_H_

#include <vector>

#include "abel/strings/internal/format.h"

FMT_BEGIN_NAMESPACE
namespace detail {

// A compile-time string which is compiled into fast formatting code.
class compiled_string {
};

template<typename S>
struct is_compiled_string : std::is_base_of<compiled_string, S> {
};

//  Converts a string literal *s* into a format string that will be parsed at
//  compile time and converted into efficient formatting code. Requires C++17
//  ``constexpr if`` compiler support.
//
//  **Example**::
//
//    // Converts 42 into std::string using the most efficient method and no
//    // runtime format string processing.
//    std::string s = abel::format(FMT_COMPILE("{}"), 42);

#define FMT_COMPILE(s) FMT_STRING_IMPL(s, abel::detail::compiled_string)

template<typename T, typename... Tail>
const T &first(const T &value, const Tail &...) {
    return value;
}

// Part of a compiled format string. It can be either literal text or a
// replacement field.
template<typename Char>
struct format_part {
    enum class kind {
        arg_index, arg_name, text, replacement
    };

    struct replacement {
        arg_ref <Char> arg_id;
        dynamic_format_specs <Char> specs;
    };

    kind part_kind;

    union value {
        int arg_index;
        basic_string_view <Char> str;
        replacement repl;

        constexpr value(int index = 0) : arg_index(index) {}

        constexpr value(basic_string_view <Char> s) : str(s) {}

        constexpr value(replacement r) : repl(r) {}
    } val;

    // Position past the end of the argument id.
    const Char *arg_id_end = nullptr;

    constexpr format_part(kind k = kind::arg_index, value v = {})
            : part_kind(k), val(v) {}

    static constexpr format_part make_arg_index(int index) {
        return format_part(kind::arg_index, index);
    }

    static constexpr format_part make_arg_name(basic_string_view <Char> name) {
        return format_part(kind::arg_name, name);
    }

    static constexpr format_part make_text(basic_string_view <Char> text) {
        return format_part(kind::text, text);
    }

    static constexpr format_part make_replacement(replacement repl) {
        return format_part(kind::replacement, repl);
    }
};

template<typename Char>
struct part_counter {
    unsigned num_parts = 0;

    constexpr void on_text(const Char *begin, const Char *end) {
        if (begin != end) ++num_parts;
    }

    constexpr int on_arg_id() { return ++num_parts, 0; }

    constexpr int on_arg_id(int) { return ++num_parts, 0; }

    constexpr int on_arg_id(basic_string_view <Char>) {
        return ++num_parts, 0;
    }

    constexpr void on_replacement_field(int, const Char *) {}

    constexpr const Char *on_format_specs(int, const Char *begin,
                                          const Char *end) {
        // Find the matching brace.
        unsigned brace_counter = 0;
        for (; begin != end; ++begin) {
            if (*begin == '{') {
                ++brace_counter;
            } else if (*begin == '}') {
                if (brace_counter == 0u) break;
                --brace_counter;
            }
        }
        return begin;
    }

    constexpr void on_error(const char *) {}
};

// Counts the number of parts in a format string.
template<typename Char>
constexpr unsigned count_parts(basic_string_view <Char> format_str) {
    part_counter<Char> counter;
    parse_format_string<true>(format_str, counter);
    return counter.num_parts;
}

template<typename Char, typename PartHandler>
class format_string_compiler : public error_handler {
  private:
    using part = format_part<Char>;

    PartHandler handler_;
    part part_;
    basic_string_view <Char> format_str_;
    basic_format_parse_context <Char> parse_context_;

  public:
    constexpr format_string_compiler(basic_string_view <Char> format_str,
                                     PartHandler handler)
            : handler_(handler),
              format_str_(format_str),
              parse_context_(format_str) {}

    constexpr void on_text(const Char *begin, const Char *end) {
        if (begin != end)
            handler_(part::make_text({begin, to_unsigned(end - begin)}));
    }

    constexpr int on_arg_id() {
        part_ = part::make_arg_index(parse_context_.next_arg_id());
        return 0;
    }

    constexpr int on_arg_id(int id) {
        parse_context_.check_arg_id(id);
        part_ = part::make_arg_index(id);
        return 0;
    }

    constexpr int on_arg_id(basic_string_view <Char> id) {
        part_ = part::make_arg_name(id);
        return 0;
    }

    constexpr void on_replacement_field(int, const Char *ptr) {
        part_.arg_id_end = ptr;
        handler_(part_);
    }

    constexpr const Char *on_format_specs(int, const Char *begin,
                                          const Char *end) {
        auto repl = typename part::replacement();
        dynamic_specs_handler <basic_format_parse_context<Char>> handler(
                repl.specs, parse_context_);
        auto it = parse_format_specs(begin, end, handler);
        if (*it != '}') on_error("missing '}' in format string");
        repl.arg_id = part_.part_kind == part::kind::arg_index
                      ? arg_ref<Char>(part_.val.arg_index)
                      : arg_ref<Char>(part_.val.str);
        auto part = part::make_replacement(repl);
        part.arg_id_end = begin;
        handler_(part);
        return it;
    }
};

// Compiles a format string and invokes handler(part) for each parsed part.
template<bool IS_CONSTEXPR, typename Char, typename PartHandler>
constexpr void compile_format_string(basic_string_view <Char> format_str,
                                     PartHandler handler) {
    parse_format_string<IS_CONSTEXPR>(
            format_str,
            format_string_compiler<Char, PartHandler>(format_str, handler));
}

template<typename OutputIt, typename Context, typename Id>
void format_arg(
        basic_format_parse_context<typename Context::char_type> &parse_ctx,
        Context &ctx, Id arg_id) {
    ctx.advance_to(visit_format_arg(
            arg_formatter<OutputIt, typename Context::char_type>(ctx, &parse_ctx),
            ctx.arg(arg_id)));
}

// vformat_to is defined in a subnamespace to prevent ADL.
namespace cf {
template<typename Context, typename OutputIt, typename CompiledFormat>
auto vformat_to(OutputIt out, CompiledFormat &cf,
                basic_format_args <Context> args) -> typename Context::iterator {
    using char_type = typename Context::char_type;
    basic_format_parse_context<char_type> parse_ctx(
            to_string_view(cf.format_str_));
    Context ctx(out, args);

    const auto &parts = cf.parts();
    for (auto part_it = std::begin(parts); part_it != std::end(parts);
         ++part_it) {
        const auto &part = *part_it;
        const auto &value = part.val;

        using format_part_t = format_part<char_type>;
        switch (part.part_kind) {
            case format_part_t::kind::text: {
                const auto text = value.str;
                auto output = ctx.out();
                auto &&it = reserve(output, text.size());
                it = std::copy_n(text.begin(), text.size(), it);
                ctx.advance_to(output);
                break;
            }

            case format_part_t::kind::arg_index:
                advance_to(parse_ctx, part.arg_id_end);
                detail::format_arg<OutputIt>(parse_ctx, ctx, value.arg_index);
                break;

            case format_part_t::kind::arg_name:
                advance_to(parse_ctx, part.arg_id_end);
                detail::format_arg<OutputIt>(parse_ctx, ctx, value.str);
                break;

            case format_part_t::kind::replacement: {
                const auto &arg_id_value = value.repl.arg_id.val;
                const auto arg = value.repl.arg_id.kind == arg_id_kind::index
                                 ? ctx.arg(arg_id_value.index)
                                 : ctx.arg(arg_id_value.name);

                auto specs = value.repl.specs;

                handle_dynamic_spec<width_checker>(specs.width, specs.width_ref, ctx);
                handle_dynamic_spec<precision_checker>(specs.precision,
                                                       specs.precision_ref, ctx);

                error_handler h;
                numeric_specs_checker<error_handler> checker(h, arg.type());
                if (specs.align == align::numeric) checker.require_numeric_argument();
                if (specs.sign != sign::none) checker.check_sign();
                if (specs.alt) checker.require_numeric_argument();
                if (specs.precision >= 0) checker.check_precision();

                advance_to(parse_ctx, part.arg_id_end);
                ctx.advance_to(
                        visit_format_arg(arg_formatter<OutputIt, typename Context::char_type>(
                                ctx, nullptr, &specs),
                                         arg));
                break;
            }
        }
    }
    return ctx.out();
}
}  // namespace cf

struct basic_compiled_format {
};

template<typename S, typename = void>
struct compiled_format_base : basic_compiled_format {
    using char_type = char_t<S>;
    using parts_container = std::vector<detail::format_part<char_type>>;

    parts_container compiled_parts;

    explicit compiled_format_base(basic_string_view <char_type> format_str) {
        compile_format_string<false>(format_str,
                                     [this](const format_part <char_type> &part) {
                                         compiled_parts.push_back(part);
                                     });
    }

    const parts_container &parts() const { return compiled_parts; }
};

template<typename Char, unsigned N>
struct format_part_array {
    format_part<Char> data[N] = {};

    constexpr format_part_array() = default;
};

template<typename Char, unsigned N>
constexpr format_part_array<Char, N> compile_to_parts(
        basic_string_view <Char> format_str) {
    format_part_array<Char, N> parts;
    unsigned counter = 0;
    // This is not a lambda for compatibility with older compilers.
    struct {
        format_part<Char> *parts;
        unsigned *counter;

        constexpr void operator()(const format_part<Char> &part) {
            parts[(*counter)++] = part;
        }
    } collector{parts.data, &counter};
    compile_format_string<true>(format_str, collector);
    if (counter < N) {
        parts.data[counter] =
                format_part<Char>::make_text(basic_string_view<Char>());
    }
    return parts;
}

template<typename T>
constexpr const T &constexpr_max(const T &a, const T &b) {
    return (a < b) ? b : a;
}

template<typename S>
struct compiled_format_base<S, enable_if_t < is_compile_string<S>::value>>
: basic_compiled_format {
using char_type = char_t<S>;

constexpr explicit compiled_format_base(basic_string_view <char_type>) {}

static constexpr const unsigned num_format_parts =
        constexpr_max(count_parts(to_string_view(S())), 1u);

using parts_container = format_part<char_type>[num_format_parts];

const parts_container &parts() const {
    static constexpr const auto compiled_parts =
            compile_to_parts<char_type, num_format_parts>(
                    detail::to_string_view(S()));
    return compiled_parts.data;
}
};

template<typename S, typename... Args>
class compiled_format : private compiled_format_base<S> {
  public:
    using typename compiled_format_base<S>::char_type;

  private:
    basic_string_view <char_type> format_str_;

    template<typename Context, typename OutputIt, typename CompiledFormat>
    friend auto cf::vformat_to(OutputIt out, CompiledFormat &cf,
                               basic_format_args <Context> args) ->
    typename Context::iterator;

  public:
    compiled_format() = delete;

    explicit constexpr compiled_format(basic_string_view <char_type> format_str)
            : compiled_format_base<S>(format_str), format_str_(format_str) {}
};

#ifdef __cpp_if_constexpr
template<typename... Args>
struct type_list {
};

// Returns a reference to the argument at index N from [first, rest...].
template<int N, typename T, typename... Args>
constexpr const auto &get(const T &first, const Args &... rest) {
    static_assert(N < 1 + sizeof...(Args), "index is out of bounds");
    if constexpr (N == 0)
        return first;
    else
        return get<N - 1>(rest...);
}

template<int N, typename>
struct get_type_impl;

template<int N, typename... Args>
struct get_type_impl<N, type_list<Args...>> {
    using type = remove_cvref_t<decltype(get<N>(std::declval<Args>()...))>;
};

template<int N, typename T>
using get_type = typename get_type_impl<N, T>::type;

template<typename T>
struct is_compiled_format : std::false_type {
};

template<typename Char>
struct text {
    basic_string_view <Char> data;
    using char_type = Char;

    template<typename OutputIt, typename... Args>
    OutputIt format(OutputIt out, const Args &...) const {
        return write<Char>(out, data);
    }
};

template<typename Char>
struct is_compiled_format<text<Char>> : std::true_type {
};

template<typename Char>
constexpr text<Char> make_text(basic_string_view <Char> s, size_t pos,
                               size_t size) {
    return {{&s[pos], size}};
}

// A replacement field that refers to argument N.
template<typename Char, typename T, int N>
struct field {
    using char_type = Char;

    template<typename OutputIt, typename... Args>
    OutputIt format(OutputIt out, const Args &... args) const {
        // This ensures that the argument type is convertile to `const T&`.
        const T &arg = get<N>(args...);
        return write<Char>(out, arg);
    }
};

template<typename Char, typename T, int N>
struct is_compiled_format<field<Char, T, N>> : std::true_type {
};

// A replacement field that refers to argument N and has format specifiers.
template<typename Char, typename T, int N>
struct spec_field {
    using char_type = Char;
    mutable formatter <T, Char> fmt;

    template<typename OutputIt, typename... Args>
    OutputIt format(OutputIt out, const Args &... args) const {
        // This ensures that the argument type is convertile to `const T&`.
        const T &arg = get<N>(args...);
        basic_format_context<OutputIt, Char> ctx(out, {});
        return fmt.format(arg, ctx);
    }
};

template<typename Char, typename T, int N>
struct is_compiled_format<spec_field<Char, T, N>> : std::true_type {
};

template<typename L, typename R>
struct concat {
    L lhs;
    R rhs;
    using char_type = typename L::char_type;

    template<typename OutputIt, typename... Args>
    OutputIt format(OutputIt out, const Args &... args) const {
        out = lhs.format(out, args...);
        return rhs.format(out, args...);
    }
};

template<typename L, typename R>
struct is_compiled_format<concat<L, R>> : std::true_type {
};

template<typename L, typename R>
constexpr concat<L, R> make_concat(L lhs, R rhs) {
    return {lhs, rhs};
}

struct unknown_format {
};

template<typename Char>
constexpr size_t parse_text(basic_string_view <Char> str, size_t pos) {
    for (size_t size = str.size(); pos != size; ++pos) {
        if (str[pos] == '{' || str[pos] == '}') break;
    }
    return pos;
}

template<typename Args, size_t POS, int ID, typename S>
constexpr auto compile_format_string(S format_str);

template<typename Args, size_t POS, int ID, typename T, typename S>
constexpr auto parse_tail(T head, S format_str) {
    if constexpr (POS !=
                  basic_string_view<typename S::char_type>(format_str).size()) {
        constexpr auto tail = compile_format_string<Args, POS, ID>(format_str);
        if constexpr (std::is_same<remove_cvref_t < decltype(tail)>,
                unknown_format > ())
            return tail;
        else
            return make_concat(head, tail);
    } else {
        return head;
    }
}

template<typename T, typename Char>
struct parse_specs_result {
    formatter <T, Char> fmt;
    size_t end;
};

template<typename T, typename Char>
constexpr parse_specs_result<T, Char> parse_specs(basic_string_view <Char> str,
                                                  size_t pos) {
    str.remove_prefix(pos);
    auto ctx = basic_format_parse_context<Char>(str);
    auto f = formatter<T, Char>();
    auto end = f.parse(ctx);
    return {f, pos + (end - str.data()) + 1};
}

// Compiles a non-empty format string and returns the compiled representation
// or unknown_format() on unrecognized input.
template<typename Args, size_t POS, int ID, typename S>
constexpr auto compile_format_string(S format_str) {
    using char_type = typename S::char_type;
    constexpr basic_string_view <char_type> str = format_str;
    if constexpr (str[POS] == '{') {
        if (POS + 1 == str.size())
            throw format_error("unmatched '{' in format string");
        if constexpr (str[POS + 1] == '{') {
            return parse_tail<Args, POS + 2, ID>(make_text(str, POS, 1), format_str);
        } else if constexpr (str[POS + 1] == '}') {
            using type = get_type<ID, Args>;
            return parse_tail<Args, POS + 2, ID + 1>(field<char_type, type, ID>(),
                                                     format_str);
        } else if constexpr (str[POS + 1] == ':') {
            using type = get_type<ID, Args>;
            constexpr auto result = parse_specs<type>(str, POS + 2);
            return parse_tail<Args, result.end, ID + 1>(
                    spec_field<char_type, type, ID>{result.fmt}, format_str);
        } else {
            return unknown_format();
        }
    } else if constexpr (str[POS] == '}') {
        if (POS + 1 == str.size())
            throw format_error("unmatched '}' in format string");
        return parse_tail<Args, POS + 2, ID>(make_text(str, POS, 1), format_str);
    } else {
        constexpr auto end = parse_text(str, POS + 1);
        return parse_tail<Args, end, ID>(make_text(str, POS, end - POS),
                                         format_str);
    }
}

template<typename... Args, typename S,
        FMT_ENABLE_IF(is_compile_string<S>::value ||
                      detail::is_compiled_string<S>::value)>
constexpr auto compile(S format_str) {
    constexpr basic_string_view<typename S::char_type> str = format_str;
    if constexpr (str.size() == 0) {
        return detail::make_text(str, 0, 0);
    } else {
        constexpr auto result =
                detail::compile_format_string<detail::type_list<Args...>, 0, 0>(
                        format_str);
        if constexpr (std::is_same<remove_cvref_t < decltype(result)>,
                detail::unknown_format > ()) {
            return detail::compiled_format<S, Args...>(to_string_view(format_str));
        } else {
            return result;
        }
    }
}

#else

template<typename... Args, typename S,
        FMT_ENABLE_IF(is_compile_string<S>::value)>
constexpr auto compile(S format_str) -> detail::compiled_format<S, Args...> {
    return detail::compiled_format<S, Args...>(to_string_view(format_str));
}

#endif  // __cpp_if_constexpr

// Compiles the format string which must be a string literal.
template<typename... Args, typename Char, size_t N>
auto compile(const Char (&format_str)[N])
-> detail::compiled_format<const Char *, Args...> {
    return detail::compiled_format<const Char *, Args...>(
            basic_string_view<Char>(format_str, N - 1));
}
}  // namespace detail

// DEPRECATED! use FMT_COMPILE instead.
template<typename... Args>
ABEL_DEPRECATED auto compile(const Args &... args)
-> decltype(detail::compile(args...)) {
    return detail::compile(args...);
}

#ifdef __cpp_if_constexpr

template<typename CompiledFormat, typename... Args,
        typename Char = typename CompiledFormat::char_type,
        FMT_ENABLE_IF(detail::is_compiled_format<CompiledFormat>::value)>
ABEL_FORCE_INLINE std::basic_string<Char> format(const CompiledFormat &cf,
                                                 const Args &... args) {
    basic_memory_buffer<Char> buffer;
    detail::buffer<Char> &base = buffer;
    cf.format(std::back_inserter(base), args...);
    return to_string(buffer);
}

template<typename OutputIt, typename CompiledFormat, typename... Args,
        FMT_ENABLE_IF(detail::is_compiled_format<CompiledFormat>::value)>
OutputIt format_to(OutputIt out, const CompiledFormat &cf,
                   const Args &... args) {
    return cf.format(out, args...);
}

#endif  // __cpp_if_constexpr

template<typename CompiledFormat, typename... Args,
        typename Char = typename CompiledFormat::char_type,
        FMT_ENABLE_IF(std::is_base_of<detail::basic_compiled_format,
                              CompiledFormat > ::value)>
std::basic_string<Char> format(const CompiledFormat &cf, const Args &... args) {
    basic_memory_buffer<Char> buffer;
    using context = buffer_context<Char>;
    detail::buffer<Char> &base = buffer;
    detail::cf::vformat_to<context>(std::back_inserter(base), cf,
                                    make_format_args<context>(args...));
    return to_string(buffer);
}

template<typename S, typename... Args,
        FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
ABEL_FORCE_INLINE std::basic_string<typename S::char_type> format(const S &,
                                                                  Args &&... args) {
    constexpr basic_string_view<typename S::char_type> str = S();
    if (str.size() == 2 && str[0] == '{' && str[1] == '}')
        return abel::to_string(detail::first(args...));
    constexpr auto compiled = detail::compile<Args...>(S());
    return format(compiled, std::forward<Args>(args)...);
}

template<typename OutputIt, typename CompiledFormat, typename... Args,
        FMT_ENABLE_IF(std::is_base_of<detail::basic_compiled_format,
                              CompiledFormat > ::value)>
OutputIt format_to(OutputIt out, const CompiledFormat &cf,
                   const Args &... args) {
    using char_type = typename CompiledFormat::char_type;
    using context = format_context_t<OutputIt, char_type>;
    return detail::cf::vformat_to<context>(out, cf,
                                           make_format_args<context>(args...));
}

template<typename OutputIt, typename S, typename... Args,
        FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
OutputIt format_to(OutputIt out, const S &, const Args &... args) {
    constexpr auto compiled = detail::compile<Args...>(S());
    return format_to(out, compiled, args...);
}

template<
        typename OutputIt, typename CompiledFormat, typename... Args,
        FMT_ENABLE_IF(detail::is_output_iterator<OutputIt>::value &&std::is_base_of<
                              detail::basic_compiled_format, CompiledFormat > ::value)>
format_to_n_result <OutputIt> format_to_n(OutputIt out, size_t n,
                                          const CompiledFormat &cf,
                                          const Args &... args) {
    auto it =
            format_to(detail::truncating_iterator<OutputIt>(out, n), cf, args...);
    return {it.base(), it.count()};
}

template<typename CompiledFormat, typename... Args>
size_t formatted_size(const CompiledFormat &cf, const Args &... args) {
    return format_to(detail::counting_iterator(), cf, args...).count();
}

FMT_END_NAMESPACE

#endif  // ABEL_STRINGS_INTERNAL_COMPILE_H_
